Tony Perkins
EF2
Media reports large steel A frame transmissions lines down, one of them square on top of a car in the northern Twin Cities metro.
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- Weather and Chasing
- Target Area
9/21/05 NOW: WI/MI/MN
- Thread starter nickgrillo
- Start date
Kurt Hulst
EF5
When supercells begin there line/bow out that usually means the storm has become primarily outflow dominate. Which usally undercuts any circulation that trys to occurr below the storm. As Jeff pointed out that it is not uncommon to get gust nados or spin ups along the gust front. So andrew basically thats the case as storms line out they gust out becoing downdraft dominate pushing the energy ahead of the cell.
nickgrillo
EF5
For a number of different reasons...
Including nocturnal boundary layer cooling (although there is some SFC-based instability still spread across southern MN) and although the threat for severe thunderstorms still continues... It'll be in the form of either damaging winds (as the storms gust out) or large hail. Often, after sunset, any isolated cells will form into a line - and then progress through the rest of the night a MCS. This, of course is not always the case, but I'm just saying...
Andrew Khan
EF5
Thanks for explaining it, Kurt, Nick and Jeff. These storms still have a number of flood warnings and severe thunderstorm warning on them, however.
Jeff Snyder
EF5
Looking at the reports, it appears that this supercell did more nontornadic damage damage than many tornadic supercells produce. There are 2 reports of tornadoes in MN, but there are many more rather remarkable reports of intense wind damage in the northern Twin Cities metro area. On radar, it looked like an HP beast with a very intense, rain-filled RFD, as it crossed the northern metro, before transitioning into an MCS as it crossed into WI.
The 0z MPX showed ~450 0-3km SRH with 2250-2500 CAPE (extrapolated to the equilibrium level since the sounding ends in the mid-levels). Given the rotation evident on radar, it MAY have been a tornado, but the times don't really match up well with radar imagery for me to suspect a tornado. I'd bet much of it is >90mph winds in the wet RFD.
Below are some of the more high-end reports...
http://kamala.cod.edu/offs/KMPX/0509220308.nwus53.html
Andrew Khan
EF5
Jeff, are you saying that there could have been a possible tornado, in the break between where the radar sounding end and begin? How can you tell what a HP/LP/Classic Supercell looks like on radar? I have occasionally been able to identify, them, but sometimes it becomes more difficult. I am interested to see if anyone has any pictures of this thing. BTW, there is still two flood warnings and one thunderstorm warning still in MN.Chris Carlson
EF1
After watching all the local news reports, the damage is fairly bad in several urban areas. From what I saw, it did not appear to be damage from a tornado. Several homes have been destroyed, several roads have been shut down, many reports and pictures of golf ball and even what appeared to be near baseball size hail, it seems nearly every road is flooded to some point, and at last count 160,000 homes were without power.
nickgrillo
EF5
"Radar sounding"? :lol: :wink:
The 0Z sounding, as Jeff mentioned, showed strong low-level shear/instability... Then, radar coinsided that with rotation on the storms where the tornadoes were reported. For the Atwater report, I'd have to say it's authentic... As radar was showing a nice low-level mesocyclone at the time of the report(s). Now, the report near the Twin Cities is certainly questionable.
You'll often notice that Classics have that "flying-V" shape to them on radar (of course, not always present)... While HPs are more grungy looking, and sometimes take on the "kidney bean" shape on radar. LPs often show very low DBZ associated with them... In turn with the 6/7/05 Kadoka, SD LP... Which was producing a tornado - And had a 40 DBZ reflectivity at the time!
Andrew Khan
EF5
Sorry about the 'Radar Sounding' lol. I thought he was saying that. Anyway, this will help me to identify supercells on radar. I need to keep studying how they look and variate.Doug Raflik
EF3
> I was sitting at 10 and 65 near Mounds View around 7pm. I watched the storm coming in and saw what could have been a tornado in the distance, but I think it was just low scud, and blowing dust. As it got right on top of me, the south side of the notch REALLY wrapped up. Beautiful, low meso, mothership with striations on the bottom. Just below the cloud base, was an arced line of scud, that was dancing around the edge of the meso like a merry go round. It was breath taking. Within the minute, the sirens went off. It was to my south, (Near Brooklyn Park) I headed south on 35w to 694, where I saw MANY power flashes to my southwest. (Fridley, New Brighton) Fruther south on 694, between 35e and 35w, I saw a bunch more power flashes and a 3 foot long branch, about a half inch in diameter, landed on my back window, while I was driving 40 mph. At that point I got very nervous. I inched my way to Maplewood where I was supposed to take pictures of a concert, only to find the whole area without power and the show postponed till thursday night.
Doug Raflik
[email protected]Chris Carlson
EF1
The latest official word is that it was a tornado. It was a F2 and now that the we can see all the damage. It's fairly widespread. Nothing too bad but over a fairly large area.
Sam Sagnella
EF5
Yeah, here's the link to the prelim survey results.
http://kamala.cod.edu/offs/KMPX/0509222139.nous43.html
Justin Turcotte
EF5
Several of my relatives homes were damaged by the storm. One very large tree on roof of aunt's home in Coon Rapids (not sure if this was in the tor path but close regardless), typical small debris in grandmother's yard also in Coon Rapids, a significant number of trees twisted and uprooted at another aunt's home in Andover with no word on the structure (NWS investigating if this area was hit by a tornado as well). Plenty of hail damage as well in the north metro but no word on that effect from the folks. Definately one of the nastier storms to hit the Twin Cities since the gorilla hail event in May 1998... impressive given it is late September in Minnesota.Similar threads
